1. Field of the Invention
The present invention relates to a slicing machine which successively slices a single-crystal semiconductor material into wafers of a predetermined thickness.
2. Description of the Prior Art
Slicing machines used to cut semiconductor material into wafer generally comprise a blade to cut a single-crystal semiconductor material in the form of a bar and a feedtable to carry it. The feedtable moves forward to set the semiconductor material in a right position for cutting and moves upward against the blade during cutting. The blade is usually an inner diameter disk cutter which cuts the bar by a tip formed along the inner-edge of the ring type disk.
These slicing machines have the following disadvantages.
(1) Before starting a slicing operation, an operator has to set a semiconductor bar mounted on the feedtable in the cutting position. To achieve this positioning, the operator has to inch the feedtable by turning on and off the motor which drives the feedtable. The operator, observing the bar and the blade, stops the bar when its front face passes the blade slightly. Once the initial position for cutting has been determined, the slicing operation starts from this position. As this initial position is determined by observation and the feedtable cannot be positioned at the operator's command, the first slice cut off from the bar has an undetermined thickness. So the first slice has to be wasted as a scrap.
(2) When the electric power is turned off, the data about the position of the feedtable at that instance is lost from the memory provided in the machine. For this reason, the relocation of the bar is required when the power is turned on again to continue the slicing operation. And this relocation is a very tedious work.